There are a number of industries that require a refractory wall. For example, industrial furnaces in which materials are treated at high temperatures, usually comprise a metal shell or a concrete outer wall that provides structural support for the entire furnace, a refractory wall positioned inside the structural metal shell or concrete outer wall, and a refractory back-up insulation wall located between the structural metal shell and the refractory wall.
A prior art refractory insulation wall is constructed from two common brick sizes. One "brick" size is a relatively large 3 feet L.times.4 feet W.times.18 inches D (length.times.width.times.depth) refractory concrete block, weighing 1,800 pounds. These 3'.times.4' blocks utilize tongue-and-groove joints for alignment. The construction of a prior art refractory insulation wall from these 3'.times.4' blocks requires the use of a crane, fork lift, or other mechanically-powered lifting apparatus for lifting the blocks and setting them in place. In addition, manpower is needed to precisely align the tongue of one 3'.times.4' block with the groove in an adjacent 3'.times.4' block. Finally, each 3'.times.4' block must be anchored to the structural metal shell or concrete outer wall.
The drawbacks of a refractory insulation wall constructed from the 3'.times.4' block is the requirement of a crane, the increased incidence of injury since one or more workers must help align the blocks during assembly, and the possibility of mismatching the blocks between courses (i.e., clearance required between the tongue and groove which is needed for proper installation makes it difficult to align and may require adjustment during and after assembly), and a system to anchor each block to the structural metal shell to maintain alignment and plumb.
The second brick size used to construct a refractory insulation wall is 9 inches L.times.4.5 inches W.times.either 2.5 inches or 3 inches D. The 9"L.times.4.5"W brick is more common than the aforementioned 3'.times.4' "brick" and is referred to as insulating fire brick (IFB). Refractory mortar is used to assemble a refractory insulation wall from the 9".times.4.5" IFB.
The primary drawbacks of this second type of brick is the requirement of skilled masons to lay the IFB, the time needed to construct a wall, and the relatively higher cost associated with the skilled labor.